Well good thing that some 6502.org visitors are
also avid NES developpers
I'm one of the mostwell-known figures in the NES developement world (I'm not a god, but people know me, and I'm a big part of that community).
Anyhow, I can tell you that trying to use the chips from the NES would be extremely futile as they are not as easy (far from that) to use as 65xx series chips, and even though the NES CPU is a 100% good 6502 core, it's not meant as a general purpose device.
I know that Kevin Horton made his "HardNES" hardware NSF (NES Sound Format) player using an NES CPU, but he's a NES guru and a general genius at this sort of video games thingy. The NES is something you write games for. Making hardware to expand it or reusing hardware from it is extremely futile. I suggest you build something out of that VIC20 since it has mostly standard chips
If you want NES development information, you can go on http://nesdev.parodius.com and find whatever there.
And for all of you who are less NES-aware, I can guarantee you that the NES is now 99.9% reverse-engineered in it's hardware configuration. Many people are now making NES games in their basement with only an EPROM programmer and a computer as their tool. Trying to re-reverse-engineer the thing would be extremely hard, considering the NES is a VERY obscure machine and everything is done with non-standard parts (unlike the Atari 2600, C64 and other machines of the time, which were proprietary but documented).
Regards,
Tennessee Carmel-Veilleux (veilleux@ameth.org